Air vent closure system

ABSTRACT

An automatic ventilator closure is described which operates on the basis of an over-pressure within the conduit leading up to the ventilator outlet. Electrical interlocks control a motor to place the closure in an open or closed condition.

FIELD OF THE INVENTION

This invention relates to the automatic opening and closing of air ventoutlets. More particularly, it relates to the detection of anover-pressure condition in an exhaust outlet in order to activate theopening of a door or flap.

BACKGROUND OF THE INVENTION

Many buildings are provided with exhaust vents to evacuate air from theinterior of the building to out-of-doors. Typical examples includeexhaust vents for residential driers and stoves.

When the ventilation system operates intermittently, if the exhaustoutlet is left in an open condition, a back-draft condition may occur.In cold climates, cold air may enter the structure, causing discomfort,condensation and heat loss.

It would, therefore, be desirable to provide an automatic mechanism foropening and closing an air exhaust outlet, according to whether or notair is being exhausted or ventilated therethrough.

A variety of prior art references have addressed this problem. Some haverelied directly on activation of the closure system by the direct meansof the physical force that the over-pressure develops when the exhaustfan is turned on. Others have relied on a powered opening mechanism thatis coupled directly to the ventilation system's fan or motor. In suchcases, the opening mechanism is operated by an electrical switch that isactivated by the electrical circuit that turns the fan motor on.Examples in the former category of direct, pressure activated systemsare:

U.S. Pat. No. 2,730,943 R. B. Klein

U.S. Pat. No. 2,739,521 W. A. Spear

U.S. Pat. No. 3,541,945 Monroe L. Wexler

U.S. Pat. No. 4,214,380 Stephen T. Meyer

U.S. Pat. No. 4,237,621 Lucien Boismenu

The use of direct mechanical force derived from an over-pressurecondition is deficient in that the weight of the closure means,generally a flap or segmented vanes, must be kept to a minimum. This, inturn, limits the amount of closing force that such closure means mayexert. Further, variations in the degree of over-pressure, as whentemporary blockages or diversions of air occur within the conduit, maycause the closure means to oscillate, and produce noise.

As mentioned above, it is also known to activate the opening and closingof doors by electric actuators in accordance with the activation of thefan motor. This arrangement has the disadvantage of requiring that anelectrical connection from the ventilator fan motor to the ventilatoroutlet be installed.

However, a combined mechanism for conveniently detecting adraft/no-draft condition in an air exhaust outlet, and activating aclosure for such a ventilator outlet in a positive fashion without beingelectrically or mechanically connected to the ventilator fan has notbeen proposed.

It is, therefore, an object of this invention to provide such amechanism.

SUMMARY OF THE INVENTION

According to the invention a closure means on an outlet for a forced airexhaust conduit is activated between an open condition when air is beingexhausted, and a closed condition when air is not being exhausted, bymeans of the combination of:

(1) an actuating motor means for positioning said closure in either aclosed or open state; and

(2) switch means for activating said motor to position said closure ineither said open or closed state

wherein said switch means is responsive to an over-pressure, or absenceof over-pressure condition in said conduit with respect to ambientpressure external to said conduit.

By a further feature of the invention said switch means is alsoresponsive to an air flow in said conduit, or absence of an air flow insaid conduit.

More particularly, the aforesaid switch means may, in a preferredembodiment, comprise:

(1) a source of electrical current for said actuating motor means;

(b 2) electrical switch means capable of switching said current to saidmotor means between "on" or "off" conditions;

(3) an over-pressure sensor system connected to activate said switch andcomprising:

(a) a bleed-outlet formed in said conduit through which air may tend toescape when said over-pressure condition exists; and

(b) a pressure-sensing means positioned to move between a first,over-pressure detecting position under the influence of an over-pressureto close said bleed-outlet and a second, no-pressure detecting positionin the absence of an over-pressure where said bleed outlet is notclosed.

whereby said electrical switch is activated by said pressure sensingmeans to control said motor means.

By a further feature of the invention said electrical switch means isalso activated by an air flow sensing means positioned to detect thepresence or absence of an air flow condition in said conduit.

By a further feature of the invention, first electrical interlock andswitching means is provided to interrupt the flow of current to saidmotor when said closure means is in a fully open position,simultaneously with said pressure sensing means being at saidover-pressure or air flow detecting position; and to permit the flow ofcurrent to said motor, so as to effect closure of said conduit, whensaid pressure sensing means indicate said no-pressure condition.

In the preferred embodiments a bleed-outlet with an inner swinging flapwhich is positioned to swing under an over-pressure condition towardssaid bleed outlet is used as the pressure sensing device to activate theswitch.

By a further feature of the invention, the said bleed-outlet may beformed in said region of said conduit exterior to said closed structurefrom which said exhaust air originates.

By a further feature of the invention, a sealing means may be providedwhich is positioned to close said bleed-outlet when an over-pressurecondition does not exist.

By a further feature of the invention the pressure sensing means, motormeans and closure may be combined in a modular unit that may attacheddirectly to the conduit outlet without further wiring.

Thus, in accordance with the invention and with further featuresdescribed below, when an exhaust fan turns on and creates anover-pressure in the air exhaust conduit, the pressure sensing meanswill be activated. In the preferred embodiment, it will move to a firstposition so as to close the bleed outlet, activating a first switchwhich supplies current to the motor means. The motor means, which may bea stepping motor or standard dc electrical motor acting through areduction drive or other arrangement of similar effect, will then openthe conduit closure. Once the closure is fully open, the interlock meansinterrupts the flow of current to the motor and holds the conduitclosure in a static, "open" mode.

With the closure fully open the over-pressure condition in the conduitwill reduce and may cause a faulty detection of the requirement to havesaid closure in the fully open position. It is for this reason that thepressure sensing means may be combined with an air flow sensing means soas to keep the said first switch in the static, open mode if air flow isdetected with only a minimal over-pressure condition.

When the exhaust fan stops, the over-pressure condition in the conduitwill drop and the air flow will stop. This causes the pressure/air flowsensing means to be deactivated. In the preferred embodiment thepressure-sensing means will move, under a spring or gravity bias, to asecond position whereby the bleed outlet is open. By this action theelectrical interlock holding the conduit closure in its "open" state isover-ridden and a second switching means commences to provide current tothe motor in a manner which causes the closure means for the conduit toclose.

A second interlock means may be provided to interrupt the flow ofcurrent to the motor, once the closure means on the conduit is in afully closing condition. This second interlock may be over-ridden andcombined with the first switch means to permit current to flow to themotor means, in a closure-opening direction, once the pressure-sensingmeans is moved by a resumption of over-pressure to its firstclosure-opening position.

An outer sealing means may be provided for the pressure sensor in theform of a flap that does not interfere with the movement of the pressuresensing means between its first and second positions. However, when thepressure sensing means is fully at its second position this sealingmeans then covers the bleed outlet. Such an arrangement is easilyprovided by utilizing an interiorly located flap for the pressuresensing means and coupling the inner flap in a symmetrical fashion to anexterior flap which serves as the sealing means. By coupling these twoflaps so that they move in unison, each will take turns closing thebleed outlet without interfering with the ability of the pressuresensing means to move between its first and second positions.

These and further features of the invention will be better understoodfrom the description of the preferred embodiments which now follows.

SUMMARY OF THE FIGURES

FIG. 1 is a schematic drawing of a conduit passing through the wall of astructure where it terminates in a motor controlled closure;

FIG. 2a and 2b show one form of pressure sensor, in open and closedconditions;

FIG. 3a and 3b shown an alternate form of pressure sensor, in open andclosed conditions;

FIGS. 4a and 4b show a further pressure sensor with a supplementarycover for the bleed outlet in the form of an external flap;

FIG. 5 is an electrical schematic for a circuit to activate the closureof an alternate linkage arrangement between the motor and closure;

FIG. 6 is a schematic depiction of an alternate linkage arrangementbetween the motor and closure;

FIG. 7 is an isometric view of an externally mountable closure modulewhich may be installed as an add-on to existing ventilation outlets; and

FIG. 8 is a further isometric view of an alternate form of slattedmodule.

SUMMARY OF THE PREFERRED EMBODIMENTS

In FIG. 1 a conduit (1) passes from the interior (2) of a structurethrough a wall (4) to the exterior (5). A source of air, such as a fan(6), intermittently supplies air, under pressure, to the conduit (1).

A closure (7) in the form of a cover is positioned at the exterior end(8) of the conduit (1) as it exits the wall (4). The closure (7) mayeither be in the form of a swinging door, or a series of rotatableslats. A motor (9) is positioned to rotate the closure (7) between open(10) and closed (11) positions through hinged linkage (26).

Current for the motor (9) is provided from a power source (not shown inFIG. (1)), which may be a battery, through wires leading to a firstpressure sensing switch (13).

The pressure sensing switch may be a piezo electric device, or otherstandard, commercial pressure sensor, such as one of the Motorola (™)series pressure sensor transducers sold under the MPX-trade mark.Alternately, the pressure sensing switch (13), conveniently may be inthe form of a position-sensitive mercury or mechanical contact switchthat is mounted in a fixed position with respect to a swinging vane (14)that is a component of the pressure sensing system. This is theconfiguration shown in greater detail in FIGS. 2a and 2b.

The vane (14) can move between open (15) and closed (16) positions. Inthe open position (15) a bleed-outlet (17) through the conduit (1) maybe exposed. In the closed position (16), this bleed-outlet (17) iscovered by the vane (14) which functions as a flap.

The switch (13), which may be of the double pole-double thrown type, ormay operate a relay allows current to flow to the motor (9) when thevane (14) is at open position (15) and the closure (1) is at closedposition (11). Current is then supplied through wires (13a) in adirection that causes the closure (1) to open.

An alternative pressure sensing switch may be utilized that relies on asingle pole optical detector and relay switch. Such optical detector ispositioned to activate the relay switch in accordance with whether thevane (14) is in its open (15) or closed (16) positions, and the relayswitch provides the function of operating the motor.

A first interlock switch (18), conveniently in the form of a contactswitch, detects when the closure (1) is in the open position (10). Itthen interrupts current to the motor (9), thus serving as an electricalinterlock. Subsequently, this first interlock switch (18) is bypassed bya closure-activating switch (19), described further below.

Friction in the motor drive, conveniently supports the closure (7) inthe open position (15), once the fully opened position is reached.

As long as the fan (6) continues to provide air to the conduit (1), theover-pressure created will hold the vane (14) in position (16) where itcloses the bleed-outlet (17). In cases where the air flow is so low asto cause uncertainty in the operation of the pressure sensing switch,reliability may be increased by providing a switching vane (40) which issuspended in the path of the air flow, and which activates in parallel asupplementary switch (41) to the pressure sensing switch (13) when itswings under the influence of air flow to a position 40a.

When the fan (6) shuts down, the over-pressure and air flow conditionwill disappear. The vane (14) is biased by its own weight, or a spring,to fall away from the bleed-outlet (17). Once in its second or openposition (15) the second pole of the pressure sensing switch (13) isactivated to provided current to the motor (9) through wires bypassingthe first electrical interlock switch (18). The closure-effecting polesof the pressure sensing switch (13) operate in complementary fashion.Each pole routes current to the motor (9) so as to correspondinglyrotate the closure (7) between the open (10) and closed positions (11).

Thus the motor (9) is fed current supplied, for example, by battery(25), through the closure activating pole of the pressure sensing switch(13) in a direction that causes the closure (7) to move to its closedposition (11). On arriving at this closed position (11), a secondfurther electrical interlock switch (20) interrupts the flow of currentto the motor (9). The pressure sensing switch (13) is wired to the motor(9) in a manner whereby the second electrical interlock switch (20) isbypassed when the vane (14) returns to the closed position (17).

The logic of this switching is shown in Table (1).

                  TABLE 1    ______________________________________             Bleed-Outlet                        Bleed-Outlet             Open       Closed    ______________________________________    Closure    SS1 = 0      SS1 = 1    Open       SS2 = 1      SS2 = 0               IS1 = 0      IS1 = 0               IS2 = 1      IS2 = 1               (Motor on, in                            (Motor off)               closing direction)    Closure    SS1 = 0      SS1 = 1    Closed     SS2 = 1      SS2 = 0               IS1 = 1      IS1 = 1               IS2 = 0      IS2 = 0               (Motor Off)  (Motor on, in                            opening direction)    ______________________________________     where the above parameters have the following definitions.     SS1 -- is the first or "opening" pole of the pressure sensing switch     SS2 -- is the second or "closing" pole of the pressure sensing switch     effecting, switch     IS1 -- is the first interlock switch in its initial state*     IS2 -- is the second interlock switch in its initial state     "0" represents an open condition     "1" represents a closed or "on" condition     *The initial state of the interlock switches are indicated because both     such switches are "on" transmission.

An electrical circuit which will carry-out these functions is shown inFIG. 5. This circuit is shown in the transition state to effect opening.

In FIG. 5 a source of dc current (25) provides current to a dc motor(9). IS1 and IS2 are single pole switches which correspond to the firstand second interlock switches. DSS1 and DSS2 are double pole switches bywhich in one position there will be a flow of current to the motor (9)in one direction and in the other position there will be a flow ofcurrent to the motor (9) in the opposite direction. The double polefunctions of the switches DSS1 and DSS2 correspond to the first andsecond sensing switches, with the added feature of providing a reversingrouting for the current to the motor. This double pole-double throwfunction may be effected through the use of a single pole switch as asingle sensing switch, and a correspondingly controlled relay.

As an optional feature, for the mechanical arrangement of the preferredpressure sensing embodiment, the vane (14) may be provided with acomplementary outlet-occupying block (21) mounted to swing with the vane(14) as shown in FIGS. 3a, b. This block will enhance the pressuresensitivity of the vane (14) and provide means to close the bleed-outletfrom entry by insects.

As a further alternative, the vane (14) may be coupled to an externalflap (21) by a spacing strut (22). When the vane (14) is in its openposition (15), the flap (21) is positioned to cover the bleed-outlet(17). This will also prevent entry of insects and cold air through thebleed outlet (17).

The flap (21) is particularly desirable when the bleed-outlet ispositioned exterior to the wall (4). However, the bleed outlet (17) maybe placed within the interior (2) of the structure. In such case, theneed for the flap (21) is not as pressing.

As an alternative arrangement for coupling the motor (9) to the closure(7) as shown in FIG. 6, the motor (9) may be mounted beneath arectangular sleeve 30 which fits on the end of the conduit 1, as shownin FIG. 7. As shown in FIGS. 6 and 7 the motor (9) may be provided witha threaded shaft (27). A thread nut (28) mounted on the shaft (27) isflexibly coupled to a linkage (28) which is flexibly coupled to thebottom of the closure (7). Initially in a position (29) corresponding tothe closure (7) being in its closed position the nut (28) is moved byrotation of the shaft (27) to a position (30a). This change in positioncauses the linkage (28) to extend outwardly, opening the closure (7) asin FIG. 7 (not shown in FIG. 6). Such a motor-linkage arrangement canconveniently be mounted beneath the conduit (1) adjacent the closure(7).

FIG. 7 shows a modular form of the invention adapted for externalattachment to existing exhaust fan outlets where the conduit (1) exitsthrough a wall (4). In this embodiment a sleeve (30) is provided to fiton a close friction basis with the end of the conduit (1) (not shown).This sleeve (30) carries the bleed-outlet (17) at a convenient position.This may be at the top (as shown) where gravity is to bias the sensingvane to assume an open condition when no over-pressure exists.Alternately, it may be located elsewhere when a spring-biasing means isprovided.

The closure 7, in the form of a hinged flap, is opened and closed by atransversely mounted motor (9) with threaded shaft (27) and linkage(28), as described above. The motor (9) is mounted beneath the sleeve(30) in order to shelter it. As well, a battery and relay module (31)may be similarly mounted.

An alternate louvered modular unit, shown in FIG. 8, may be readilyfitted in place by consumers with a minimum of effort, on acomplementary circular conduit. The interior region behind the louvers(40) in this embodiment will provide the required space for the motorand necessary linkages.

From the foregoing it will be seen that an automatic closure mechanismcan be provided for an air exhaust outlet, in accordance with theprinciples exemplified by the preferred embodiments, which isindependently capable of opening and closing, according to whether thereis an exhaust draft or not. Such a unit in modular format may beconveniently installed by consumers as an "after-fitted" feature toclothes driers, stoves and oven exhausts. Once installed, it willprovide protection from the discomfort and energy costs of exterior airinfiltration when the exhaust fan is no longer operating.

The foregoing has been a description of preferred, exemplaryembodiments. The invention in its most general and more particularaspects is further described and defined in the claims which now follow.

The embodiments of the invention in which an exclusive property isclaimed as follows:
 1. A closure means on an outlet for a forced airexhaust conduit which is positioned to convey air from within a closedstructure to a region exterior to such structure, comprising:(1) anactuating motor means for positioning said closure in either a closed oropen state in response to electrical current provided by an electricalsource; (2) electrical switch means for providing said motor with saidelectrical current; (3) an over-pressure sensor system responsive to anover-pressure condition in said conduit with respect to ambient pressureexternal to said conduit and connected to activate said switch, . .suchsensor system comprising: (a) a bleed-outlet formed in said conduitthrough which air tends to escape when said over-pressure conditionexists; and (b) a pressure-sensing means positioned to swing between afirst, over-pressure detecting position closing said bleed-outlet, and asecond, no-pressure detecting position where said bleed-outlet is notclosed.!..Iadd.; and (4) an air flow sensing means which is positionedto detect the presence or absence of air flow within saidconduit.Iaddend.,wherein said electrical switch is activated by said ..pressure sensing means.!. .Iadd.over-pressure sensor system and by saidair flow sensing means in parallel .Iaddend.to control said motor means.Iadd.to open said closure in the presence of either airflow or anover-pressure condition and to close said closure in the absence of bothair flow and an over-pressure condition.Iaddend..
 2. A closure means asin claim 1 wherein said . .electrical switch means is also activated inparallel by an air flow sensing means which is positioned to detect thepresence or absence of air flow within saidconduit.!..Iadd.over-pressure sensor system comprises:(a) a bleed-outletformed in said conduit through which air tends to escape when saidover-pressure condition exists; and (b) a pressure-sensing meanspositioned to swing between a first over-pressure detecting positionclosing said bleed-outlet, and a second, non-pressure detecting positionwhere said bleed-outlet is not closed.Iaddend..
 3. A closure means as inclaim 1 or 2 wherein first electrical interlock and switching means isprovided to interrupt the flow of current to said motor when saidclosure means is in a fully open position, and to permit the flow ofcurrent to said motor, in a direction so as to effect closure of saidconduit, when said pressure sensing means is at said no-pressureposition.
 4. A closure as in claim 3 wherein a second interlock andswitching means is provided to interrupt the flow of current to saidmotor, once the closure means on the conduit is in a fully closedcondition, and to permit current to flow to said motor means, in aclosure-opening direction, once the pressure-sensing means is activatedby an over-pressure condition in said conduit.
 5. A closure means as inclaim . .1 or.!. 2 wherein a secondary bleed-outlet closure means isprovided which is positioned to close said bleed-outlet when anover-pressure condition does not exist within said conduit.
 6. A closuremeans as in claim 4 wherein a secondary bleed-outlet closure means isprovided which is positioned to close said bleed-outlet when anover-pressure condition does not exist within said conduit.
 7. A closureas in claims 1 or 2 in the form of a modular unit incorporating abattery as said electrical source that may be fitted at the exiting endof said . .closure.!. .Iadd.conduit. .Iaddend.
 8. A closure as in claim3 in the form of a modular unit, incorporating a battery as saidelectrical source, that may be fitted at the exiting end of said ..closure.!. .Iadd.conduit. .Iaddend.
 9. A closure as in claim 4 in theform of a modular unit, incorporating a battery as said electricalsource, that may be fitted at the exiting end of said . .closure.!..Iadd.conduit. .Iaddend.
 10. A closure as in claim 5 in the form of amodular unit, incorporating a battery as said electrical source, thatmay be fitted at the exiting end of said . .closure.!. .Iadd.conduit..Iaddend.
 11. A closure as in claim 6 in the form of a modular unit,incorporating a battery as said electrical source, that may be fitted atthe exiting end of said . .closure.!. .Iadd.conduit. .Iaddend.